Power amplifier Triode Made by the Marconi Osram Valve Company, with a capability of 100 Watts. Using Molybdemum electrodes and Oxide coated filament designed specifically for use in output stages of power amplifiers.
A pair of valves could be used in push pull, class AB with low distortion, generating 200 Watts.
The valve became well known in PA amplifiers. It was also used in the modulator chain of the Marconi SWB8 and SWB10 transmitters.
As it was used in Cinema amplifiers it became known as the 'Talkie Valve'.